The present invention relates generally to semiconductor packaging and in particular to a semiconductor module with an imbedded heat spreader.
The semiconductor industry is constantly producing smaller and more complex semiconductors, sometimes called integrated circuits or chips. This trend has brought about the need for smaller chip packages with smaller footprints, higher lead counts, and better electrical and thermal performance, while at the same time meeting accepted reliability standards.
In recent years a number of microelectronic packages have been produced to meet the need for smaller chip packaging. One such package is referred to as a chip scale package (CSP). CSPs are so called because the total package size is similar or not much larger than the size of the chip itself. Typically, the CSP size is between 1 and 1.2 times the perimeter size of the chip, or 1.5 times the area of the die. One example of a CSP is a product developed by TESSERA(copyright) called xe2x80x9cMICRO BGAxe2x80x9d or xcexcBGA. In a CSP, the semiconductor has a set of bond pads distributed across its surface. A first surface of an insulating, flexible film is positioned over the semiconductor surface. Interconnect circuitry is positioned within the film. Electrical connections are made between the interconnect circuitry and the semiconductor bond pads. Solder balls are subsequently attached to a second surface of the film in such a manner as to establish selective connections with the interconnect circuitry. The solder balls may then be attached to a printed circuit board.
CSPs may be used in connection with memory chips. Memory chips may be grouped to form in-line memory modules. In-line memory modules are surface mounted memory chips positioned on a circuit board.
As memory demands increase, so does the need for increased memory capacity of in-line memory modules. A need has also arisen for materials and methods that lead to increased performance by more closely matching the coefficient of thermal expansion of the materials used in these memory modules. Examples of such in-line memory modules are single in line memory modules or SIMMs and dual in-line memory modules or DIMMs. DIMMs have begun to replace SIMMs as the compact circuit boards of preference and essentially comprise a SIMM wherein memory chips are surface mounted to opposite sides of the circuit board with connectors on each side.
A problem with in-line memory modules is that adding more chips to the circuit board spreads out the placement of the chips on the circuit card and therefore requires reconfiguration of the circuit card connectors and their associated connections on the motherboard, which means replacing the memory card and in some cases the motherboard.
Another problem with current in-line memory modules is that a separate heat spreader must be positioned across a set of memory chips. The heat spreader adds cost to the assembly process and adds significant weight to the module.
In view of the foregoing it would be highly desirable to provide a semiconductor module that overcomes the shortcomings of prior art devices.
According to the invention there is provided a semiconductor module comprising a heat spreader, at least two semiconductors thermally coupled to the heat spreader, and a plurality of electrically conductive leads electrically connected to the semiconductors. The leads may form part of a flexible circuit at least partially attached to the heat spreader, where at least one of the electrically conductive leads is common to both of the semiconductors. The two semiconductors may be directly bonded onto opposing side walls of the heat spreader.
According to the invention there is also provided a method of making a semiconductor module. A plurality of electrically conductive leads are provided, preferably on a flexible circuit or tape. Two semiconductors are then electrically connected to the leads. The semiconductors are then thermally coupled to a heat spreader. This may be done by mounting the semiconductor directly to opposing walls of the heat spreader. The leads may then be soldered to a printed circuit board. The module may also be anchored to the printed circuit board by means of a fastening mechanism.